Gastroenterology

Gastroenterology

Volume 133, Issue 1, July 2007, Pages 244-255
Gastroenterology

Basic–liver, pancreas, and biliary tract
Glucagon-Like Peptide-1 and Its Receptor Agonist Exendin-4 Modulate Cholangiocyte Adaptive Response to Cholestasis

https://doi.org/10.1053/j.gastro.2007.04.007Get rights and content

Background & Aims: Cholangiopathies are characterized by progressive dysregulation of the balance between proliferation and death of cholangiocytes. In the course of cholestasis, cholangiocytes undergo a neuroendocrine transdifferentiation and their biology is regulated by neuroendocrine hormones. Glucagon-like peptide-1 (GLP-1), secreted by neuroendocrine cells, sustains β-cell survival in experimental diabetes and induces the neuroendocrine transdifferentiation of pancreatic ductal cells. GLP-1 receptor (GLP-1R) selective agonist exendin-4 is used in humans as a novel therapeutic tool for diabetes. The aim of this study was to define if GLP-1 modulates cholangiocyte biologic response to cholestasis. Methods: Expression of GLP-1R in cholangiocytes was determined. Effects on cholangiocyte proliferation of the in vitro and in vivo exposure to GLP-1 or exendin-4, together with the intracellular signals, were then studied. Synthesis of GLP-1 by cholangiocytes and the effects of GLP-1R blockage on their growth were also determined. Results: Cholangiocytes express the GLP-1 receptor, which is up-regulated in the course of cholestasis. GLP-1 and exendin-4 increase cholangiocyte growth both in vitro and in vivo. The GLP-1R signal is mediated by the phosphatidyl-inositol-3-kinase, cAMP/Protein Kinase A, and Ca2+-CamKIIα but not by the ERK1/2 and PKCα pathways. Proliferating cholangiocytes synthesize GLP-1: neutralization of its action by GLP-1R antagonist blunts cholangiocyte response to cholestasis. Conclusions: GLP-1 is required for the cholangiocyte adaptive response to cholestasis. Cholangiocytes are susceptible to the activation of GLP-1R and respond with increased proliferation and functional activity. Exendin-4 availability for employment in humans and these data may open novel perspectives for the medical treatment of cholangiopathies.

Section snippets

Materials

Reagents were purchased from Sigma Chemical (St. Louis, MO) unless otherwise indicated. Intracellular cyclic adenosine 3′, 5′-monophosphate (cAMP) and D-myo-Inositol 1,4,5-triphosphate (IP3) levels were determined with RIA kits purchased from Amersham (Arlington Heights, IL). Antibodies for immunoblotting were purchased from Santa Cruz Biotechnologies Inc. (Santa Cruz, CA), unless differently indicated. The antibody anti-GLP1R was purchased by Alpha Diagnostic (San Antonio, TX); the antibody

Cholangiocytes Express the GLP-1R, That Is, Up-regulated in the Course of Cholestasis

Both RT-PCR and immunoblots show the presence of GLP-1R in cholangiocytes (Figure 1). Interestingly, the quantitative analysis of the immunoblotting data demonstrate that GLP-1R expression is up-regulated after 1-week BDL (Figure 1, right panel). The semiquantitative evaluation of GLP-1 mRNA expression confirms such changes in mRNA expression (Figure 1, left panel).

GLP-1R Activation Stimulates Cholangiocyte Proliferation In Vitro

The in vitro incubation of normal rat cholangiocytes with increasing doses of GLP-1 determined a progressive increase in cell

Discussion

The current study provides evidence that GLP-1 is a potent stimulator of cholangiocyte proliferation, and that it is required for the proliferative response of the biliary epithelium to cholestasis. In particular, this study shows that: (1) cholangiocytes express the GLP-1R that is up-regulated in the course of cholestasis; (2) activation of the GLP-1R by GLP-1 or by the selective agonist exendin-4 stimulates normal rat cholangiocyte proliferation; (3) these changes in cell growth are mediated

References (54)

  • M. Ishii et al.

    Isolation and morphological characterization of bile duct epithelial cells from normal rat liver

    Gastroenterology

    (1989)
  • G. LeSage et al.

    Insulin inhibits secretin-induced ductal secretion by activation of PKC alpha and inhibition of PKA activity

    Hepatology

    (2002)
  • M.E. Rothenberg et al.

    Processing of mouse proglucagon by recombinant prohormone convertase 1 and immunopurified prohormone convertase 2 in vitro

    J Biol Chem

    (1995)
  • D. Alvaro et al.

    Regulation and deregulation of cholangiocyte proliferation

    J Hepatol

    (2000)
  • D. Alvaro et al.

    Estrogen receptors in cholangiocytes and the progression of primary biliary cirrhosis

    J Hepatol

    (2004)
  • E. Gomez et al.

    cAMP-dependent protein kinase and Ca2+ influx through L-type voltage-gated calcium channels mediate Raf-independent activation of extracellular regulated kinase in response to glucagon-like peptide-1 in pancreatic beta-cells

    J Biol Chem

    (2002)
  • M. Marzioni et al.

    Ca2+-dependent cytoprotective effects of ursodeoxycholic and tauroursodeoxycholic acid on the biliary epithelium in a rat model of cholestasis and loss of bile ducts

    Am J Pathol

    (2006)
  • M.M. Belcheva et al.

    Mu-opioid receptor-mediated ERK activation involves calmodulin-dependent epidermal growth factor receptor transactivation

    J Biol Chem

    (2001)
  • K. Hirata et al.

    Regulation of Ca(2+) signaling in rat bile duct epithelia by inositol 1,4,5-trisphosphate receptor isoforms

    Hepatology

    (2002)
  • K. Shibao et al.

    Loss of inositol 1,4,5-trisphosphate receptors from bile duct epithelia is a common event in cholestasis

    Gastroenterology

    (2003)
  • G. Alpini et al.

    Ursodeoxycholate and tauroursodeoxycholate inhibit cholangiocyte growth and secretion of BDL rats through activation of PKC alpha

    Hepatology

    (2002)
  • Annual Report of the U.S. Organ Procurement and Transplantation Network and the Scientific Registry for Transplant Recipients

    (2001)
  • T. Roskams et al.

    Neuroendocrine features of reactive bile ductules in cholestatic liver disease

    Am J Pathol

    (1990)
  • P.L. Brubaker et al.

    Minireview: glucagon-like peptides regulate cell proliferation and apoptosis in the pancreas, gut, and central nervous system

    Endocrinology

    (2004)
  • D.J. Drucker

    Glucagon-like peptides: regulators of cell proliferation, differentiation, and apoptosis

    Mol Endocrinol

    (2003)
  • M.S. Fineman et al.

    Effect on glycemic control of exenatide (synthetic exendin-4) additive to existing metformin and/or sulfonylurea treatment in patients with type 2 diabetes

    Diabetes Care

    (2003)
  • A. Bulotta et al.

    Cultured pancreatic ductal cells undergo cell cycle re-distribution and beta-cell-like differentiation in response to glucagon-like peptide-1

    J Mol Endocrinol

    (2002)
  • Cited by (0)

    The authors of this manuscript declare no conflict of interest to disclose.

    Supported by MIUR Grant 2005067975_004 to Dr. Marzioni and by the Università Politecnica delle Marche Intramural Grants ATBEN00205 to Dr. Benedetti and ATMAR01105 to Dr. Marzioni; a VA Merit Award, a VA Research Scholar Award, the Dr. Nicholas C. Hightower Centennial Chair of Gastroenterology from Scott & White to Dr. Alpini, and the NIH Grant DK062975 to Dr. Alpini.

    View full text